The Tecnifibre Duramix HD 1.35 tennis string has a multifilament construction & a Silicon Pyrogene Lubritec additive that reduces elongation & improves durability by up to 40%. Multifilaments have been reinforced with polyester to provide the user with high quality product that offers comfort & top performance. The string has a gauge of 15L (1.35mm) & the set of it provides 40ft (12.2m), which is enough to re-string one racket.